Because of the way the regular expression spans scanlines, it requires the width of the target image in order to be fully generated. However, the sub-regexp for each scanline can be (and are) generated in advance.

When a Imager::Search::Pattern object is created, the driver method pattern_lines is called to generate the scanline regexp for the search pattern.

Returns a reference to an ARRAY containing the regexp in string form, or dies on error.